1. Field of the Invention
The present invention relates to aircraft surface guidance systems (SGS) and, in particular, to a communications interchange for transmitting airport feature data to a conformal display system (e.g., head-up display (HUD)) on an aircraft.
2. Technical Background
There is considerable interest in enhancing surface guidance for aircraft. After an aircraft lands on a runway at an airport, the next step is to taxi the aircraft to a desired destination such as a passenger-loading/unloading gate. A pilot can easily become confused or lost amid the many runways, taxiways, ramps, and buildings that make up an airport. The problem is more significant at large airports and is particularly significant at night when the multitude of lights can make it more difficult to taxi the aircraft to the desired destination.
Efficient taxi operations save time and money. With airports becoming more crowded, aircraft often spend considerable time taxiing between runways and gates. Taxi time is even longer if the pilot makes a wrong turn, becomes lost, or blunders onto the wrong runway or taxiway. In addition, a wrong turn or navigation blunder can cause delays for other aircraft at the airport.
One feature of an airport surface guidance capability is the presentation of airport features such as runways and taxiways that are readily made available to the pilot. One approach to present such feature information is on a head-up display (HUD) that is displayed in the forward line of sight of the pilot looking out the front windshield of the aircraft. The pilot typically enters or selects a taxi path that has been approved by ground controllers. The taxi path or route is then displayed on the HUD. The pilot can view the features displayed on the HUD as being overlaid on the surface features the pilot can normally see through the windshield. However, in poor visibility conditions, the pilot can still view the airport features displayed on the HUD. The airport features give a pilot situational awareness of where the aircraft is relative to the selected taxi path.
A key aspect to a practical avionics implementation for surface guidance must generally include a communications bus or data link for transmitting the large amounts of data required to adequately represent airport features on a display screen. An obstacle for the practical implementation of an airport feature display system is the requirement to clearly display airport features, preferably with taxi instructions and other useful symbology conformal to the pilot""s view out the front windshield. Data representing airport features can also consume large amounts of memory. The problem is more acute since the data for many airports must be stored in memory. In addition, prior airport feature display systems require a correspondingly high-speed communications bus to transmit the airport feature data to a display system (e.g., HUD). This requirement, coupled with the fact that many avionics systems have limited data storage capability and do not have high-speed buses, have stymied efforts to implement airport features on the existing HUD systems on many aircraft. One approach for displaying airport features has been to upgrade aircraft avionics systems with new equipment that has large data storage capability and high speed data buses. However, these systems must be designed, certified, integrated with the exiting avionics suite, and installed. All this makes such an upgrade very costly and, therefore, this approach is economically infeasible for many aircraft.
Any airport feature display system should be adequate not only to accomplish the task of displaying airport features, but to also make the displayed features useful and the system cost-effective. It is also desirable to design an airport feature display system that may be retrofit into existing aircraft avionics systems at minimal cost.
The continuing goal, therefore, is to find ways to reduce costs, reduce taxi errors, reduce taxi time, and improve airport efficiency.
To address the goals stated above and other goals, the inventive airport feature display system comprises a unique data interchange method for facilitating the commnunication of airport feature data through conventional data buses without the need to design or install new high speed data buses. For retrofit applications, the airport feature display system is compatible with many existing HUD systems with minimal modification.
According to one aspect of the present invention, the airport feature display system is integrated as an extension of the flight management system (FMS) which provides the enroute planning function for the aircraft. The FMS is already installed in many aircraft and the FMS comprises many of the components required to implement the airport feature display system of the invention. For example, an FMS comprises a processor, data storage devices, a user interface, and is in communication with multiple display systems such as a HUD.
Another aspect of the invention is reduced bandwidth requirements for communicating the data representative of airport features to the HUD. This is important for implementing a cost-effective feature display system on existing aircraft. Many existing communications buses between an FMS and a HUD do not have sufficient bandwidth to communicate the feature data. One example of such a bus is the electronic flight instrument system (EFIS) bus that typically communicates data between the FMS and the HUD. The present invention significantly reduces the necessary bandwidth. A high-resolution position coordinate for an airport monument is transmitted to the HUD. A high resolution coordinate requires two words of Aeronautical Radio, Inc. (ARINC) data. The invention transmits the remaining data coordinates as one word that represent a high resolution position, but are referenced to the airport monument (i.e., reference point). The invention thereby effectively reduces the required bandwidth by approximately one half. This is sufficient to enable the use of existing communication buses and significant cost savings.
It is clear that the invention is a significant improvement over the prior art systems. Further, those skilled in the art recognized that the invention is not limited to use with an FMS. Other processors, display screens, and data entry devices may be used to practice the invention.
Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described in the detailed description which follows, the claims, as well as the appended drawings.
It is to be understood that the foregoing description is exemplary of the invention only and is intended to provide an overview for the understanding of the nature and character of the invention as it is defined by the claims. The accompanying drawings are included to provide a further understanding of the invention and are incorporated and constitute part of this specification. The drawings illustrate various features and embodiments of the invention which, together with their description, serve to explain the principals and operation of the invention.